Lead press



Oct. 25, 1932. C, E. BENNETT LEAD PRESS Filed Dec. 8, 1931 i T'. I

INVENTOR.

Patented oer. 2s, 1932 UNITED STATES PATENT.i OFFICE CHARLES E. BENNETT, OF PATERSON, NEW JERSEY, ASSIGNOR TO THE OKONITE COMPANY, F PASSAIC, NEW JERSEY, A CORPORATION 0F NEW JERSEY LEAD PRESS Application led December 8, 1931. Serial No. 579,690.

My invention is directed to an improvement in lead presses wherein lead in a molten-or a ysemi-molten condition is being handled, and

has for one of its objects the provision of an 5 apparatus so constructed and arranged that the difficulties heretofore experienced with this type of apparatus are overcome.

In order that my invention may be clearly understood I will describe the same in connection with the application of a lead sheath to the exterior of an insulated cable, although it is to be understood that this example is merely by way of illustration and is not in tended to limit my invention to this use.

In the application of lead sheaths to insulated cables as practiced heretofore the insulated conductor is fed through a press which is equipped with a suitable die, the lead being supplied to this press in a molten or semisa molten condition. In connection with such apparatus it is usual to employ a vat or tank of molten metal heated in' any suitable fashion and when the apparatus is in use the metal from this tank is forced under very high S5 pressure to the die of the press to provide a sheath of lead about the insulation of the conductor.

It is important not only for economical reasons but for operating requirements that the R0 wall of. the sheath thus applied shall be of uniform thickness. In order that the metal may be kept at the proper temperature as it is being applied to the cable the die block mustbe heated. Heretofore it has been customary to employ gas jets about the die block of the press. It is necessary also, before the apparatus is started, that the die block be heated and consequently it is customary to apply these gas jets to the die block for 40 a. suitable length of time prior to operation of the apparatus to enable the block to be raised to the desired temperature before the molten metal is fed thereto.

As above mentioned very high pressures are employed in such machines in forming the sheath about the cable and great care, therefore, must be exercised in heating the die block to insure that it shall be heated uniformly to prevent displacement of the dies. Difficulty has been experienced heretofore in this respect and for this reason the gas jets have been made adjustable so that their position with respect to the die block may be varied in an effort to compensate for unequal distribution of the heat with consequent displacement of the dies. All this necessitates the use of skilled operators and even then the results are far from satisfactory, in that the texture of the sheath is not always uniform and the dies become displaced, resulting in a so sheath the wall of which is not of uniform thickness.

The present invention provides for the heating of the die block electrically by employing suitable magnet coils to the exterior of the die block, these coils being connected to a suitable source of alternating current, means beingprovided whereby the temperature of the die block is controlled automatically.

By extensive tests I have found that a sheath produced by my apparatus has a more uniform wall and is of more uniform texture than sheaths produced with prior apparatus.

In the accompanying drawing I have shown my apparatus more or less diagrammatically.

Referring to the drawing iu detail, l designates a tank containing the molten metal.

Overlying the tank or vat 1 is a plunger 8`0 or piston 2 carried by a cross-head 3 in turn mounted on suitable uprights 4 the lower en ds of which are anchored in a suitable fashion.

Below the vat or tank 1 is a cross-head 85 5 which may be suitably mounted on the uprights 4. This cross-head is adapted to be raised by a hydraulically operated piston 6.

The construction of this part of the apparatus is well known so that I have made no attempt to illustrate the same in great detail.

Intermediate the vat l and the cross-head 5 is the die block made up of two sections 7 and 8 and containing, as will be understood, suitable dies, the cable which is to be sheathed passing through these dies. This also is well known apparatus and therefore it is unnecessary for me to illuslo@ trate the interior construction of the die block.

In operation the piston 6 rises moving the cross-head 5, the die block and the tank 1 upwardly so that the piston 2 forces the molten metal out of the vat or tank and into the die block under tremendous pressure.

9 and 10 designate magnet coils applied to the exterior of the two sections 7 and 8, respectively, of the die block. Alternating current for energizing these magnet coils may be supplied by a motor generator set 11 for example or other suitable source.

Each of the sections 7 and 8 of the die block is equipped with thermo-couple 13 connected to thermo-couple relays 14 which relays in turn are adapted to control the contactors 15.

16v designates a conductor common to both magnet coils 7' and.8, and this conductor, by means of a switch 17, is adapted to be connected to a 110 volt circuit or to a 55 volt circuit, whereby current at either of these voltages can be supplied to the magnet coils. In addition each coil is equipped with a switch 18 whereby either coil may be cut in and out independently of the other.

In operation the thermo-couple relays 14, contactors 15 and switches 18 are in closed position. The switch y17 is thrown so as to close on the contact 19 thereby closing a 110 f volt circuit to the two magnet coils 9 and 10. 60 cycle current may be used. When the magnet coils 7 and 8 are thus energized the die block sections 7 and 8 ofthe press will be subjected to the action of an alternating magnetic field to raise the temperature of the block to the desired degree mainly by the hysteresis effect of said field. I have found that a run of about thirty minutes is suiiicient to heat the die block to around 350 F. For the sake of economy the switch 17 may then be thrown to close on the contact 20 thereby connecting the magnet coils 9 and 10 to a 55 volt circuit to reduce the field iux and to maintain the die block'at a substantially constant temperature 4of say 350 F. or at whatever tem perature the block was heated to initially. As a matter of fact it has been found by eX- tensive tests that one or the other of the switches 18 may be opened so as to cut out one of the magnet coils.

It will'be appreciated of course that the thermo-couples 13 heretofore referred to are adapted, through the relays 14 and contactors 15 to automatically control the circuits of the magnet coils 7 and 8 so as to hold the temperature of the diel block Within certain predetermined limits.

What I claim is 1. In the heating of lead press die blocks, the method which consists in subjecting the block to the laction of an alternating magnetic 5 ield to raise the temperature of the block to the desired degree mainly by the hysteresis eii'ect of said field, and then reducing the iield iuX to maintain the block substantially at said temperature.

2. In combination a lead press die block, a pair of magnet coils about said block, asource of alternating current for said coils, the energizing of said coils subjecting the block to the action of an alternating magnetic field to raise the temperature of the block to the desired degree mainly by the hysteresis effect of said field, and means for deenergizing either one of said coils to reduce the flux of said magnetic field to maintain the block substantially at said temperature.

3. In combination a lead press die block, magnet coils about said block, means for supplying alternating current to said coils initially to subject the block to the action of an alternating magnetic field to raisethe tem- This specification signed this 3rd day of December, 1931.

CHARLES E. BENNETT. 

